In Caulfield application Ser. No. 485,828 filed 4-18-83, now U.S. Pat. No. 4,498,740, there is described a three dimensional image system in which a hologram is written from an input signal such as a computer-generated signal or a television signal or the like, wherein object or information beams scan in three dimensions representing x, y, z coordinates, to present to a holographic recording medium small segments of an information beam corresponding to a three dimensional image. According to that invention, a resulting hologram may be created or written much faster and more efficiently than in the prior art.
In one embodiment of that invention, scanning mirrors scan a laser beam across a holographic medium in x and y coordinates and a lens scans in those dimensions and focuses in the third or z coordinate, the lens moving closer to or further from the holographic medium to express the third dimension. Such lens focuses the object or information beam close to the holographic medium, the point being closely adjacent in front of the medium, behind it, or even within it. With the focal point closely adjacent to the holographic medium, exposure of the individual elements of the medium is kept to small individual areas and not spread across the entire medium.
The present invention is an improvement over the invention in that prior patent application.